No internet access on laptop or android phone

The internet connection to main computer is via an ethernet cable, and is fine. I have had little or no connection to my laptop and phone for several days. When I run the troubleshooter on laptop the wifi signal comes back on and I can connect to the net for about 30 secs. then it goes again. I connected the laptop to the router with an ethernet cable and it was fine. Has anyone got advice for me?

I have reset the router, no change. I don't know if I've got a dual band router, but the problem started suddenly, one day fine the next no internet. It comes back for a minute or two when I run the troubleshooter, but then goes again.